Air Plan Approval; Connecticut; 2017 Base Year Emissions Inventory for the 2015 8-Hour Ozone National Ambient Air Quality Standards

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R01-OAR-2025-0076; FRL-12691-01-R1]</DEPDOC> <SUBJECT>Air Plan Approval; Connecticut; 2017 Base Year Emissions Inventory for the 2015 8-Hour Ozone National Ambient Air Quality Standards</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is proposing approval of State Implementation Plan (SIP) revisions submitted by the State of Connecticut that relate to the 2015 Ozone National Ambient Air Quality Standards (NAAQS). The SIP revisions are for the Greater Connecticut and the Connecticut portion of the New York-Northern New Jersey-Long Island, NY-NJ-CT ozone nonattainment areas. The intended effect of this action is to propose approval of submittals which include a 2017 base year emissions inventory for the 2015 Ozone National Ambient Air Quality Standard. This action is being taken under the Clean Air Act. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Written comments must be received on or before May 7, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R01-OAR-2025-0076 at <E T="03">https://www.regulations.gov,</E> or via email to <E T="03">lillis.patrick@epa.gov.</E> Or comments submitted at <E T="03">Regulations.gov</E> , follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">Regulations.gov</E> . For either manner of submission, the EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( <E T="03">i.e.,</E> on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit <E T="03">https://www.epa.gov/dockets/commenting-epa-dockets.</E> Publicly available docket materials are available at <E T="03">https://www.regulations.gov</E> or at the U.S. Environmental Protection Agency, EPA Region 1 Regional Office, Air and Radiation Division, 5 Post Office Square—Suite 100, Boston, MA. EPA requests that if at all possible, you contact the contact listed in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section to schedule your inspection. The Regional Office's official hours of business are Monday through Friday, 8:30 a.m. to 4:30 p.m., excluding legal holidays and facility closures due to COVID-19. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Patrick Lillis, Air and Radiation Division (Mail Code 5-MI), U.S. Environmental Protection Agency—Region 1, 5 Post Office Square, Suite 100, Boston, Massachusetts 02109-3912; tel. (617) 918-1067, or by email at <E T="03">lillis.patrick@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA. <HD SOURCE="HD1">Table of Contents</HD> <EXTRACT> <FP SOURCE="FP-2">I. Background and Purpose</FP> <FP SOURCE="FP-2">II. Description of State's Submittals</FP> <FP SOURCE="FP-2">III. The EPA's Evaluation of Connecticut's SIP Submittals</FP> <FP SOURCE="FP1-2">A. 2017 Base Year Emissions Inventory</FP> <FP SOURCE="FP1-2">1. Point Source Emissions</FP> <FP SOURCE="FP1-2">2. Nonpoint Source Emissions</FP> <FP SOURCE="FP1-2">3. On-Road Mobile Source Emissions</FP> <FP SOURCE="FP1-2">4. Non-Road Source Emissions</FP> <FP SOURCE="FP1-2">5. Biogenic Emissions</FP> <FP SOURCE="FP1-2">6. EPA's Evaluation of the Base Year Emissions Inventory</FP> <FP SOURCE="FP-2">IV. Proposed Action</FP> <FP SOURCE="FP-2">V. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Background and Purpose</HD> Ozone is one of the six common air pollutants identified in the Clean Air Act. Ground-level ozone forms when nitrogen oxides (NO <E T="52">X</E> ) and volatile organic compounds (VOC) react in the presence of sunlight. Referred to as ozone precursors, these two pollutants are emitted by many types of pollution sources, including motor vehicles, power plants, industrial facilities, and nonpoint  <SU>1</SU> <FTREF/> sources. Scientific evidence indicates that adverse human health effects occur following exposure to ozone. These effects are more pronounced in children and adults with lung disease. Breathing air containing ozone can reduce lung function and inflame airways, which can increase respiratory symptoms and aggravate asthma or other lung diseases. In 1979, in response to this scientific evidence, EPA promulgated the first ozone NAAQS, the 0.12 parts per million (ppm) 1-hour ozone NAAQS. <SU>2</SU> <FTREF/> <FTNT> <SU>1</SU>   Nonpoint sources are also sometimes referred to as area sources. </FTNT> <FTNT> <SU>2</SU>  See 44 FR 8202 (Feb. 8, 1979). </FTNT> EPA has strengthened the ozone NAAQS over the years. In 1997, EPA promulgated a revised ozone NAAQS of 0.08 ppm, averaged over eight hours, which it determined was more protective of public health than the 1979 standard. <SU>3</SU> <FTREF/> In 2008, EPA revised the 8-hour ozone NAAQS from 0.08 to 0.075 ppm. <SU>4</SU> <FTREF/> In 2015, the Agency further strengthened the 8-hour ozone NAAQS to 0.070 ppm. <SU>5</SU> <FTREF/> <FTNT> <SU>3</SU>  See 62 FR 38856 (July 18, 1997). </FTNT> <FTNT> <SU>4</SU>  See 73 FR 16436 (Mar. 27, 2008). </FTNT> <FTNT> <SU>5</SU>  See 80 FR 65292 (Oct. 26, 2015). </FTNT> Effective August 3, 2018, the EPA designated as nonattainment any area that was violating the 2015 8-hour ozone NAAQS based on the three most recent years (2014-2016) of air monitoring data. <SU>6</SU> <FTREF/> With that rulemaking, the Connecticut portion of the New York-Northern New Jersey-Long Island NY-NJ-CT area was originally designated as a moderate ozone nonattainment area. This area is herein referred to as the Connecticut portion of the NY-NJ-CT area. Additionally, in that rulemaking, the Greater Connecticut area was originally designated as a Marginal ozone nonattainment area. Effective November 7, 2022, the EPA reclassified the Greater Connecticut area under the CAA from “Marginal” to “Moderate” for the 2015 8-hour ozone NAAQS. <SU>7</SU> <FTREF/> Areas that were designated as moderate nonattainment were required to attain the 2015 8-hour ozone NAAQS no later than August 3, 2024, based on 2021-2023 monitoring data. Effective July 25, 2024, the EPA published a final rule granting a voluntary reclassification request to redesignate the Connecticut portion of the NY-NJ-CT area to Serious nonattainment for the 2015 8-hour ozone NAAQS. <SU>8</SU> <FTREF/> And effective July 29, 2024, EPA published a final rule granting a voluntary reclassification request to redesignate the Greater Connecticut area to Serious nonattainment for the 2015 8-hour ozone NAAQS. <SU>9</SU> <FTREF/> Serious areas are required to attain the 2015 8-hour ozone NAAQS as expeditiously as practicable, but no later than nine years from the date of the initial designation as nonattainment, <E T="03">i.e.,</E> by August 3, 2027. <SU>10</SU> <FTREF/> While EPA has since reclassified both nonattainment areas in Connecticut to Serious for the 2015 8-hour ozone NAAQS, Connecticut must still meet the CAA requirements applicable to Marginal ozone nonattainment areas. <FTNT> <SU>6</SU>  See 83 FR 25776, 25792 (June 4, 2018). </FTNT> <FTNT> <SU>7</SU>  See 87 FR 60897 (October 7, 2022). </FTNT> <FTNT> <SU>8</SU>  See 89 FR 60314 (July 25, 2024). </FTNT> <FTNT> <SU>9</SU>  See 89 FR 60827 (July 29, 2024). </FTNT> <FTNT> <SU>10</SU>  See 40 CFR 51.1303 </FTNT> This proposed rule addresses only the base year inventory requirements related to the Marginal nonattainment classification. The CAA and its implementing regulations—in particular, the 2015 ozone NAAQS SIP Requirements Rule, <SU>11</SU> <FTREF/> codified at 40 CFR part 51, subpart CC—establish several requirements for ozone nonattainment areas. Section 172(c)(3) of the CAA, which applies generally to states with areas classified as nonattainment for any NAAQS, requires submission of comprehensive, accurate, and current inventories of actual emissions from all sources of relevant pollutants in Marginal nonattainment areas. <SU>12</SU> <FTREF/> Specific to areas classified as Marginal ozone nonattainment, section 182(a)(1) requires states to submit a base year inventory of ozone precursors (NO <E T="52">X</E> and VOC). <FTNT> <SU>11</SU>   See 83 FR 62998 (Dec. 6, 2018). The SIP Requirements Rule established implementation requirements for the 2015 ozone NAAQS, including requirements for base year emissions inventories. </FTNT> <FTNT> <SU>12</SU>  See 42 U.S.C. 7502(c)(3). </FTNT> Emissions inventories provide data that inform a variety of air quality planning tasks. States use emissions inventories to establish baseline emissions levels, calculate emissions reduction targets needed to attain the NAAQS, determine emissions inputs for ozone air quality modeling analyses, and track emissions over time to determine progress toward achieving air quality and emissions reducti ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 28k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━